JPH02264668A - Induction heater with closed magnetic path - Google Patents

Abstract

PURPOSE:To generate the large quantity of heat even in the deep part of an object to be heated and to realize a device with the small number of coils by covering the object with a soft magnetic body and covering the circumference of the soft magnetic body with a material around which an eddy current or displacement current flows. CONSTITUTION:When an alternating current is made to flow in an exciting coil 2, the eddy current or displacement current repeats a positive rotation and an inverse rotation in the period of the alternating current around a ring soft magnetic substance 3. By properly selecting a material 4 in which the eddy current or displacement current flows, a part of the eddy current advances from the material 4 into an object 1 to be heated, and it returns to the material 4 through the comparatively deep part. The phenomenon is generated in all parts to be gaplessly covered with the material 4 in which the eddy current or displacement current of the object 1 flows. Thus, the eddy current centralizingly flows to the deep part of the object 1. Consequently, even in the deep part of the object 1, the comparatively large quantity of heat can be generated.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is applicable to induction heating for cases where the epidermis is deeper than that for metals, particularly for induction heating of the human body for the purpose of thermal treatment of cancer. This invention relates to an induction heating device that generates a relatively large amount of heat even in the deep part of an object to be heated, and that generates no heat in areas that do not require heat generation.

(Prior Art) Electromagnetic induction heating of the human body for the purpose of thermal treatment of cancer, that is, electromagnetic induction hyperthermia, has been attracting attention in recent years. This is revolutionary in terms of treating cancer without causing any damage to the human body.

As a conventional technique, as shown in FIG. 6, there is a device in which a solenoid is wound around an object to be heated and a current is passed therethrough. In this device, due to the physical properties of eddy current, much of the heat is collected on the surface of the object to be heated, making it difficult to generate heat deep within the object. That is, when the tumor ggJ tissue is located deep in the human body, it is difficult to treat it. In this case, it is also difficult to prevent heat from being applied to tissues that should not generate large amounts of heat or that do not need to generate heat.

As a solution to these points, Special Publication No. 62-38
Devices such as those described in Japanese Patent No. 179 and Japanese Patent No. 197073/1982 have been reported. These devices are
This is extremely effective compared to the solenoid-based device described above. However, Special Publication No. 62-38179
In the device described in the publication, due to the Biot-Savart law and the influence of eddy currents, the alternating magnetic field rapidly attenuates as it moves away from the coils or magnetic poles that create the alternating magnetic field. Therefore, the object to be heated has the disadvantage that considerably more heat is generated near the coil or magnetic pole than in the center. To solve this problem, this device is designed to change the positions of the coil and magnetic pole during heating. Also,
This device requires four or more coils, which adds complexity to the device. In the device described in Japanese Patent Publication No. 62-197073, calculation results have been reported that when the object to be heated is a homogeneous cylinder, a partial temperature rise is observed in the center. In this case, the eddy current that should be concentrated in the center may end up spreading above and below the plane where the coil is located.

(Problems to be Solved by the Invention) The present invention is designed to easily generate a relatively large amount of heat even in the deep part of the object to be heated in induction heating, and to prevent and reduce heat generation in unnecessary parts. The idea is to make the device practical with the number of coils.

(Means for Solving the Problems) Now, the configuration will be explained: (a) An object to be heated 1 is covered with an annular soft magnetic material 3 around which two excitation coils are wound.

(0) The object to be heated is placed around the annular soft magnetic material 3!
Cover the gap between the two parts with a material 4 through which eddy current or displacement current can flow, without creating any gaps.

(c) Current generation source 5 having the function of flowing alternating current
is connected to the excitation coil 2.

The device is set up as described above. Note that the annular soft magnetic body 3 is
As long as it fulfills the role of forming a closed alternating current magnetic path around the object to be heated 1, the shape may be arbitrary, and may be interrupted in the middle (also, both the outer ring and the inner ring do not necessarily have to be perfect circles). A toroidal coil 6 may be used instead of the annular Q soft magnetic body 3 around which the excitation coil 2 is wound.Furthermore, the number of excitation coils 2 and toroidal coils 6 may basically be -1, but they may be increased. No. The material 4 through which eddy current or displacement current can flow needs only to have no gap between it and a part of the surface of the object to be heated I, and between the annular soft magnetic material 3, the exciting coil 2, and the toroidal coil 6. It doesn't matter if there is a gap between them.

(Function) When the device is configured as described above and an alternating current is passed through the excitation coil, the eddy current or displacement current repeats reverse rotation and reverse rotation around the annular soft magnetic body 3 at the cycle of the alternating current. By appropriately selecting a substance 4 through which eddy current or displacement current can flow, a part of the eddy current enters the heated object 1 from the substance 4, passes through a relatively deep part, and returns to the substance 4 again. .

This phenomenon occurs in all parts of the object to be heated 1 that are tightly covered with the substance 4 through which eddy current or displacement current can flow. Therefore, eddy current flows in a concentrated manner in the deep part of the object l to be heated.

As a result, a relatively large amount of heat is generated even in the deep part of the object to be heated. As shown in Figure 5, when the object to be heated is a homogeneous cylinder with an electrical constant equivalent to that of a muscle, three-dimensional field theory calculations show that the heat generation m in the center is approximately It reaches about 1/4.

In addition, the object to be heated that is not completely covered with substance 4
In a part of the area, the eddy JF3 flow does not enter and no heat is generated.

Therefore, parts of the heated object l that do not need to generate heat need not be completely covered with the substance 4, and if a liquid is used as the substance 4 through which eddy current or displacement current can flow, by replacing it, A rise in temperature near the surface of the object to be heated 1 can be suppressed.

(Example) Example 1 With the configuration shown in Figure 1, The annular soft magnetic body 3 is made of nickel-based ferrite.

The excitation coil 2 is wound several times around the annular magnetic body 3 (.

A liquid is used as the material 4 through which eddy current or displacement current flows.

The current generation source 5 uses a high frequency power source and an impedance matching device.

The surface of the object to be heated 1 is cooled by refluxing an appropriate amount of liquid.

Embodiment 2 In FIG. 2, a toroidal coil 6 is used in place of the annular soft magnetic body 3 around which the excitation coil 2 is wound, which is shown in Embodiment 2.

Embodiment 3 FIG. 3 shows Embodiment 3, in which the material 4 through which eddy current or displacement current can flow further limits the area where there is no gap with the object 1 to be heated, and heat generation is suppressed in areas 8 where heat generation is unnecessary. I'm aiming to suppress it.

In this case, only when an annular soft magnetic body 3 is used, the excitation coil 2 can be placed outside the substance 4 through which eddy current or displacement current can flow.

Example 4 FIG. 4 shows Example 4.

In order to suppress heat generation in parts 8 that do not require heat generation, the object to be heated l
An insulator 7 is pasted on a part of the surface.

Example 5 In Example 1, The dimensions and shape are axially symmetrical according to FIG.

As the object to be heated, a material (hereinafter referred to as a phantom) having an electrical constant equivalent to that of muscle is selected.

The substance 4 through which eddy current or displacement current can flow is 0.02
[%] Use saline solution.

Excitation coil 2 is wound eight times.

The frequency of the high frequency power source is 13.56 [Mz].

Effective value is 0. A current of 5 [A] is passed through the excitation coil.O The surface of the phantom is kept at a temperature 1 to 2 degrees C] lower than the initial temperature during muddying by circulating an appropriate amount of saline solution.

Note that the experimental results in this case will be described in the next section (Effects of the Invention).

Example 6 In Example 5, as described in Example 4, the insulator 7 is attached to a part of the phantom. However, the material of the insulator is vinyl chloride with a thickness of 1 mm.

The part where vinyl chloride is pasted is r = 0, z = 0 in the cylindrical coordinate system.
-600≦θ≦60 when is the center of the phantom
° −10 [cm] <z<10 [cm].

Note that the experimental results in this case will be described in the next section (Effects of the Invention).

(Effect of the invention) The experimental values of Examples 5 and 6 prove the effects of the invention.

The experimental data of the temperature increase after 1 hour in the case of Example 5 is shown in FIG. The measurement point is z=0, rw in the cylindrical coordinate system.
With point o as the center of the phantom, z=o [cm],
r=0. 2. 4. 6. 8 [cm].

For comparison, a similar experiment was conducted using an induction heating device using a solenoid as shown in FIG. 6, and the experimental data is also shown. During heating, the surface of the object to be heated l is
The heated object 1 is kept at a temperature 2 to 3 [℃] lower than the initial temperature.
The frequency of the excitation current was also the same.

Looking at this, it can be seen that this device generates a relatively large amount of heat even deep within the body.

The results of the temperature rise after 1 hour in the case of Example 6 are shown in FIG. Measurement points are z=o [cm], θ=O[0], r=
0. 2. 4. 6. 8 [cm] and 2-0 [cm
], θ=180['l, r=2. 4. 6゜8 [c
m].

Looking at this, you can see that the temperature rise on the side where PVC is pasted is suppressed.

From the above, it is easy to generate a relatively large amount of heat even in the deep parts of the object to be heated, to prevent heat generation from unnecessary parts, and to make it possible to realize a device with a small number of coils. The effects of the present invention were verified.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the present invention FIG. 2 is a perspective view of Embodiment 2 of the present invention FIG. 3 is a top view of Embodiment 3 of the present invention FIG. 4 is a top view of Embodiment 4 of the present invention Figure 6 is a cross-sectional view of an induction heating device using a thread/id, which was used for comparison of experimental data. Experimental data FIG. 8 shows other experimental data 1 of the present invention, object to be heated 2, excitation coil 3, annular soft magnetic body 4, eddy 21. Current or displacement? Substance 5 through which U current can flow, current generation source 6, toroidal coil 7, insulator 8, unnecessary parts that generate heat

Claims (1)

[Claims] 1. (a) An annular soft magnetic material 3 around which an excitation coil 2 is wound is placed over the object to be heated 1. (b) Cover the annular soft magnetic material 3 with a material 4 through which eddy current or displacement current can flow, without creating a gap at least in part between it and the object to be heated 1. The induction heating device 2 with a closed magnetic path characterized by the above configuration, the induction heating device with a closed magnetic path according to claim 1, using a toroidal coil 6 instead of the annular soft magnetic material 3 around which the excitation coil 2 is wound. 3. The induction heating device 4 with a closed magnetic path according to claim 1 or 2, wherein the substance 4 through which an eddy current or displacement current can flow is a liquid whose temperature is lower than that of the object to be heated 1, and the object to be heated 1 is a living body. Claim 1 or Claim 2
Alternatively, the induction heating device 5 according to claim 3, the induction heating device 6 having a closed magnetic path according to claim 3 or 4, wherein the substance 4 through which eddy current or displacement current can flow is saline, The induction heating device with a closed magnetic path according to claim 3 or 4, wherein an insulator 7 is prepared for pasting on a part.